This invention relates to an apparatus for feeding fiber tufts to a carding machine, a roller card unit, an opener, a cleaner or a similar type of fiber processing machine. The apparatus has a fill chute of generally rectangular cross section into which the fiber material is introduced at the top through a pneumatic duct joined to the fill chute at the wide side thereof. The fiber material is withdrawn from the fill chute at the bottom thereof. An airstream passes through the fill chute and is withdrawn through air outlet openings provided in the fill chute.
In practice fill chutes are used for making a fiber lap which is introduced as the input material for openers, cleaners, carding machines or tuft feeders. An air/tuft mixture is blown into the fill chute which contains air outlet openings constituted by perforated plates, slots, air-pervious fabrics, comblike structures or the like through which the air may exit from the fill chute. The fiber tufts are deposited in the chute to form a tuft column therein. The fill chutes have a certain depth which determines the thickness of the fiber lap withdrawn from the fill chute and a width which corresponds to the working width of the after-connected (downstream) processing machine.
German Offenlegungsschrift (non-examined published application No. 2,628,120) discloses a single-chute apparatus which, for improving the transverse distribution of the fiber tufts over the width of the feeder, has mechanisms to generate an alternating transverse airstream. It is a disadvantage of such an arrangement that it is complex and does not result in satisfactory distribution of the fiber tufts.
In tuft feeders which have an upper or reserve chute upstream of the feed chute, such as used in the EXACTAFEED FBK model, manufactured by Trutzschler GmbH & Co. KG, Monchengladbach, Federal Republic of Germany, transversely to the direction of discharge of the produced fiber lap, the tuft/air mixture is blown into a chute having apertures provided by a comblike structure. Since the fiber column situated in the feed chute and separated from the airstream is constantly withdrawn from below, the comlike construction is zonewise exposed. The tuft-carrying air may have easy access to those locations, resulting in an obturation of the apertures. Fiber tuft mounds accumulating above the comblike structure are blown away by the transverse air flow. It is possible that during operation the fiber tuft density is on the feed side different from that on the opposite side. Such differences remain constant and can practically not be compensated for.
For a high-requirement, single-chute feeding with high accuracy, the earlier-noted transverse charging cannot be used. In prior art constructions funnellike structures are used which gradually change from the circular cross section of the inlet duct into a rectangular shape, corresponding to the dimensions of the feed chute. Such funnels may be of bent construction to change a horizontal tuft flow into a vertical direction in which the deposition of the tufts in the feed chute takes place. The funnel constructions can have only small angles to achieve any useful fiber tuft distribution. Such a structural arrangement, however, often requires a prohibitively large inlet flow space. Such solutions are furthermore unsatisfactory in any event because it has been repeatedly found that changes in the flow direction occur which are often unpredictable and are not reversible: Once the material flow has chosen one side of the chute as the preferred side, it cannot be deflected therefrom. Also, the twist provided in the supply duct irreversibly determines the flight direction of the fiber tufts upon entrance into the distributor funnel. Further, it has been attempted to influence the flow within the duct with flow guiding devices such as deflectors, and also to reduce the effect of the duct bends on the flight of the fiber tufts within the conduits. The results, however, have been far from satisfactory.